Op Ed: What Do “Mastered for iTunes” and “Sound Check” Do To Music Listening?

One way or another, Apple is involved in a whole lot of the music to which people listen. Here, writer David Dodson considers what that means (and similar issues with other digital music listening beyond Apple, like Spotify. Photo CC-BY) Yutaka Tsutano.

What does it mean to “master for iTunes?” Apple tripped that question with the launch of a suite of utilities and sound-processing algorithms intended to master music for their codecs and software, rather than more generically as would be done with the CD. More significantly, what does it mean that an increasing number of music listeners experience all music through Apple’s software as the final gateway to their ears? In our first look at this issue, we welcome guest writer and producer Primus Luta (David Dodson). He tests this issue the only way that really matters: with his ears.

There’s so much to say, in fact, that almost each line here of David’s conclusions is up for potential discussion and debate. That to me isn’t a red flag for posting – quite the opposite, it’s an invitation. So we consider this the beginning, not the end, of this conversation. -PK

The announcement of Apple’s new Mastered for iTunes suite caught me at a serendipitous time, as I prepped the first release on my new label. In fact, the day of the announcement came right in the midst of reviewing masters for the release. It’s an interesting situation for a compilation release, in which styles range from ambient to muddy beats. Finding a good balance that keeps them all flowing together is an art in and of itself. But it would seem Apple has that all solved with their Master for iTunes droplet. Drag the high-quality files to the droplet, and presto-chango — out come files that all play perfectly in iTunes.

Well, that’s the claim, but is it mastering or encoding? To their credit, in the documentation Apple explains that their 32-bit process manages to encode from high-res audio without leaving a dithered footprint. Ed.: “Dithering” is the addition of adding small amounts of noise to compensate for errors that can occur in downsampling from greater bit depth to less – it’s used in image processing as well as in sound. According to Apple, their use of greater bit depth in the intermediary file prevents aliasing and clipping, and thus they don’t need to use dithering. -PK Apple’s tools aren’t the only way to do this. Most pro audio editors can achieve the same, but often people are ripping MP3s or AACs in their media players, so it is an important distinction. It still begs the question: why go down to CD specifications, especially while making the point of noting their process results in a quality better than CD’s or CD rips? Ed.: The greater bit-depth is only an intermediary file; eventually delivery is not only compressed, but at specifications set by the CD. Greater resolution and bit depth are limited to the mastered files, not to what the listener ultimately hears.

The most important question, though, is how does it sound? If you send a song to be mastered, you expect in general to get back a song that sounds different than the one with which you started. Generally, this difference is in perceived overall volume, but also can include changes to dynamics and other touches. So what changes does the Master for iTunes droplet make to your files? Well, none: it just encodes them. They describe the process as such:

The Droplet creates an AAC audio file from an AIFF or WAVE source file by first generating a CAF (Core Audio File) rendered with an iTunes sound check profile applied to the file. If the sample rate of the source file is greater than 44.1 kHz, it’s downsampled to 44.1 kHz using our mastering-quality SRC. Next, it uses this newly-rendered CAF to render a high-quality AAC audio file. Once the final AAC audio file is generated, the intermediary CAF is deleted.

The key part relating to how your files sound is the “iTunes sound check profile applied to the file.” Rather than changing the volume gain in the file, metadata information is used to tell the playback device how to play it. What the documentation does not tell you is what or how this information is determined.

Reviewing masters involves listening on many different systems. I like to listen on studio monitors, a small boombox, a consumer surround sound theatre system, laptop speakers, desktop computer with headphones and, of course, in a portable media player with various headphones. I’ve also added a cloud-based stream to that mix — and doing that is what brought me to the experiment I conducted.

I uploaded a test master to the the cloud and was comparing listening to it and iTunes, when I noticed a rather huge discrepancy in volume. At first, I figured they were just set to different levels, but upon checking both were at their max. So I went to play my reference song, which currently is the title track from Monolake’s new album Ghosts (I tend to try to keep my reference material relatively contemporary.) The volumes on this track between applications were more or less the same. Meanwhile, my test master, which was playing pretty much on par with the Monolake track from the cloud, played significantly lower in iTunes.

That was when I remembered Sound Check. I wasn’t on my normal listening computer and never bothered to see if Sound Check had been enabled, but sure enough, when I looked the preference was checked.

Ed.: I actually had some difficulty getting a solid answer, but consulting with Apple-following journalist Jim Dalrymple of The Loop, we believe that the default setting is off in iTunes for Mac and Windows and on iOS. If someone has a different answer to this, I’d love to hear it. What you can tell about it is what Apple has documented in support document HT2425, namely, Sound Check operates track-by-track, not album-by-album, operates in the background, and computes and stores non-destructive normalization information in ID3 tags. It works exclusively with .mp3, .AAC, .wav, and .aiff file types, and gain increases occur before the built-in iTunes Limiter. That also means you should consider the iTunes Limited as part of this process.

As soon as I disabled it, the volume was consistent across players. This inspired me to test how Sound Check was affecting other files, and so, going through my iTunes library, I built up a sample set of 25 songs to test the effects of Sound Check:

This was all done by ear, and while my ears aren’t what they used to be, I’m willing to guess if you tested, your results would be similar. Ed.: You should also be able to investigate the actual ID3 data, but in this case, perceived volume may be more interesting anyway, and the effect isn’t necessarily subtle.

About halfway through, I thought it’d be good to confirm these findings with numerical tests, but then I started noticing a pattern. Almost everything gets turned down, some more extremely than others — the most extreme example being the Nine Inch Nails track. The two tracks that get turned up are both archival recordings, and so it makes sense that they are at a lower volume. The vinyl rip from Pharoah Sanders would likely have gotten turned down, as well, save for the fact that vinyl rips are re-mastered to raise their volumes. Same goes for the live Stevie Wonder boot.

The stand-outs are the ones which Sound Check has no affect on, each of which was released within the last two years. The Tori Amos track comes from her last orchestral album. Because of the result, I tested two other selections by her on either side of the advances of digital technology, both of which get turned down. The track “Blood Roses,” like “Night of the Hunters,” features no drums but still gets turned down, as the mixing for the album is definitely rock-influenced and so the harpsichord falls on the loud side.

Stellar OM Source’s track is of the ambient drone variety, also without drums. But the Monolake track is techno, full of drums and crunching distortions, yet it remained unaffected by Sound Check. (It’s also worth noting that the Powell track, which also has prominent drums, is only barely turned down by Sound Check.) Because “Ghosts” is one of my reference tracks, I had previously done an analysis of it. I noted that, despite peaking at the max of 0 dB, its RMS only averages out at -14.5 dB. I’ve done this type of analysis for a number of modern tracks and this is unusually low. Typically, drum- and bass- heavy tracks manage to hit around -10 dB RMS with some going as high as -6 dB RMS.

The results for the Monolake track led me to hypothesize that what Sound Check was actually doing was applying an RMS limit on tracks of around -15 dB (with a +/- that I haven’t calculated yet). Anything below that gets turned up and anything above that gets turned down (with the precaution that turning up never results in clipping by going above the 0 dB max). This was confirmed when I normalized one of my test master’s to an RMS of -15 dB. This version of the track, when played in iTunes with Sound Check enabled, played at the same volume as with Sound Check disabled.

Where an object of mastering is to create a version of a song which plays at the optimum level across playback devices, where iTunes is understood as rapidly becoming a primary application for playback, and where Sound Check is often enabled as a preference in iTunes, it stands to reason that those producing masters today should be working to create versions of songs for which Sound Check does not need change the levels. As such, mastering for iTunes can be understood as creating a quality master which has an average RMS of -15 dB.

Prior to this, the primary barrier for the levels of a master was the 0 dB max limit to prevent clipping. Within that, the RMS levels could fall anywhere, which is the freedom that gave way to the loudness wars. The so-called “loudness wars” refer to the increase in compression to produce greater perceived loudness, as tracked over the rise of big FM radio and the CD through the 80s, 90s, and today. Two songs with a max of 0 dB can have extreme differences in volume based on the RMS. Production and mixing tricks, especially with the heavy use of dynamics processors like compressors, can squash a song, allowing the overall volume to be raised incredibly. Using these techniques, it’s entirely possible to create a mix (not a master) which has a max level of -4 dB but an RMS of -10 dB. If you master that track, raising the max, to 0 dB, the RMS level will push close to -6 dB. When this file is played in iTunes with Sound Check enabled, however, it’s going to be turned down to -15 dB RMS which will be below the -4 dB max level that it started with.

The potential of adopting this as a standard is an end to the loudness wars as we’ve known them. As the above example shows, doing everything you can to push a song to the max ends up having the opposite effect. So rather than worry about loudness, producers and mixing engineers can return to focusing on getting good, clean mixes of songs. Mastering engineers can also worry less about pushing the volume to the max and focus on bringing the best out of the mixes.

Incidentally, the system for producing tracks that comply to this have long existed in the mastering world, thanks to Bob Katz and the K system of level metering. Using the K-14 system of metering for mastering (and producing and mixing) can ensure that engineers are not pushing their mixes too loud.

There are, however, some negatives which can be attributed to the adoption of such a standard. Because of the headroom afforded by digital, in the last decade, the creative use of volume has increased. “Loud” has new musical meaning, and the tools utilized to maximize loudness normally in mastering are being introduced during production to create effects. An example of this is the pumping effect of side-chain compression on drums. This can be quite appealing creatively even when (and perhaps because) it pushes to levels of distortion. Creating this effect without clipping is easily managed with a limiter at the end of the signal chain. However, creating this effect below -15 dB is not so straightforward, and the results won’t necessarily be the same.

For the mastering of multi-song projects there are other issues. Over the course of an album, dynamic shifts between songs can help to carry the mood of the project. One wouldn’t necessarily want all of the tracks to have the same -15 dB RMS; ideally, that would be reserved for the loudest song and the others mixed under that accordingly. It presents a challenge, but it is manageable. What’s nice about this type of limit is that, unlike the 0 dB max limitation, going over it does not necessarily result in destructive clipping, so there’s still a dynamic range within which to work. It’s also worth noting that the Sound Check process can be applied to an album to ensure consistency in listening.

One has to hope that, should this become a standard, new creative ways of working within these parameters will be born. To be clear, -15 dB RMS, while not the loudest, can sound great for a great mix. Just listen to the Monolake track if you want proof. Getting people to adopt to it is a challenge, but I think the incentive to adopt will be there once artists realize that the more they push the volume, like their mother, the more Sound Check will turn the volume down.

As a footnote, I thought to test how Sound Check treated what was previously considered the most perfect album from a mixing mastering perspective – Steely Dan’s Aja. In iTunes, Sound Check turns “Peg” down. So it’s not just your bass heavy-beats that could be affected by this. Also, it’s not just iTunes and not just Sound Check. Replay Gain is a similar tool found in other media players. Spotify also has similar limiting for its streaming services. These things will likely show up in more playback applications as time goes on so adopting to this now is a pretty safe bet. Sure, your tracks may not sound the loudest when tested without these services, but with good mixes, they will still sound good, regardless. “Good” is far more important than “loud.”

I’m still on the fence, though. In general, I’m not a fan of auto volume control. Adopting a mastering standard that caters to them just seems wrong, even if I am (for the most part) on the side of ending the loudness wars. And, again, on the creative side, I’m very concerned. A decade of loudness wars in many ways has changed our sense of sound possibilities, and signals pushed into the red — well, I kind of like those, when they’re done creatively. People talking about the loudness wars are usually talking about traditional rock and pop music being squashed and absent of dynamics. But we’re at a point now where there are other genres for whom pushing into the red can be seen as more valuable than dynamic range. It’s a completely different school of thought and need not be shut down (or turned down) because of an antiquated sense of norm.

Great research and summary.
Since some months there is an international standard in place which is called EBU R128 (European Broadcasting Union). K-weighting was one influence, ITU-BS.1770-2 was another one (which is incorporated in the USA “calm act”), and this EBU R128 is changing EVERYTHING among European Broadcasters. Public an private stations are committing themselfs to EBU R128 which means to mix towards -23LUFS as opposed to the “old” -9dBFS paradigma. Many meters and plugins nowadays conform to EBU R128, and the EBU group responsible for R128 is also in contact with Apple to talk about adaptions to “Mastered for iTunes”.
Please also do not forget about “Replay Gain” which is incorporated into many encoders and software players and is working towards -17dB K-weighted. If someone is interested in even more details please pm or mail me, we are a public broadcaster in Austria and contributed to EBU R128.
Best regards and thanks for this article.

Great research and summary.
Since some months there is an international standard in place which is called EBU R128 (European Broadcasting Union). K-weighting was one influence, ITU-BS.1770-2 was another one (which is incorporated in the USA “calm act”), and this EBU R128 is changing EVERYTHING among European Broadcasters. Public an private stations are committing themselfs to EBU R128 which means to mix towards -23LUFS as opposed to the “old” -9dBFS paradigma. Many meters and plugins nowadays conform to EBU R128, and the EBU group responsible for R128 is also in contact with Apple to talk about adaptions to “Mastered for iTunes”.
Please also do not forget about “Replay Gain” which is incorporated into many encoders and software players and is working towards -17dB K-weighted. If someone is interested in even more details please pm or mail me, we are a public broadcaster in Austria and contributed to EBU R128.
Best regards and thanks for this article.

markLouis

“He tests this issue the only way that really matters: with
his ears”

If the only thing that matters is your ears, if there are
no principles only subjective hearing, then don’t worry about anything. Even if everything you hear is garbage, then
after three days of listening your “ears” will become acclimated to garbage and
garbage will become the environment and then you will like
garbage. And what difference does it
make? You are talking about Apple. Apple is a corporation. Even if you held some allegiance to one or
another principle, so what? What are you
going to do? Disagree with a corporation? Fight Apple?
Get real.

Puma Klement

Dear markLouis, please mind that in this case it’s not about David Dodson’s legendary objective hearing ability but a method of him testing and describing the changes in perceived volume certain audio files used for reference undergo when played with different settings offered by a software media player (that has been adopted by a huge amount of people as their way to experience music on a daily basis – which arouses a great deal of interest in how said media player alters music played through it for everyone who’s into producing, publishing and enjoying music for/with a public of some sort.)

You’re definitely right about fatigue and accustoming of one’s sense of hearing as it is exposed to any kind of static sound environment (be it at a garbage dump or within the elysian fields) and the subjective perception of sound by the individual.
But since it’s a matter of one’s brain to process and associate sound cultural marks can be overcome ( so one’s “ears” are not doomed 🙂 ), a good rest revives worn out hearing and by years and years of intent and mindful listening, passionate working with sound and a steady flow of information through sensitive communication one’s subjective perception of sound will broaden to a range that allows being able to make pretty well informed assumptions about how similarly (or at least comparably) structured neuronal networks deal with all the noise.

Throw in some heavy number crunching, psychological and neurological research done by universities, corporations and state intelligence and the documented experiences of freaky musicians who played music for the last 35.000 years…

…and there is something to be said about how we as a species hear even if it’s the latest insights of a single individual into how iTunes encodes a mastering WAV of the next Monolake release.

In reply to “What are you going to do?”:
I know from an economic and philosophical standpoint a megacorporation can be seen as a single entity (a bit like like swarm intelligence but with human individuals as its agents) that is not bound to ethics as they apply to humans and therefore can’t be questioned nor bothered by a human individual.
But here a corporation (Apple it is) seems to question the actions of other corporations (major labels in the music industry), not by means of moral but technology mixed with marketing to increase dominance in a certain market.

Alas! 🙂 the question begging to be answered here is not “What are you going to do?” but “WTF is going on? Are the Loudness Wars going to end ?!?!?!? Does Apple have to decrease the overall volume of its software/devices in order to squeeze more hours out of their batteries or what?”

so…You, Sir, get real because it’s the only difference You can make 🙂
Have a good one!

markLouis

Isn’t this issue vastly more simple than these long-winded (mine included) comments imply?

1) If it’s an issue of principle, then people like Gail Zappa and Neil Young are right and we just need a radically different, much higher standard for audio files/audio playback. (But that seems impossible because it would cost a lot more for devices and consumers at large seem satisfied with the status quo.)

2) Since it is effectively subjective then, there’s little to worry about because trivial tweaks to the status quo mean nothing to a) drunks in clubs listening to bad sound systems; b) cruisers in cars with giant bass speakers in the trunk shaking the car; and c) yuppies playing a ‘soundtrack for their life’ through $2 ear-buds.

I get grumpy (sorry) because I LIKE philosophical discussions but stuff like this is like faux philosophy, because it is all so straightforward that the real discussion isn’t philosophy or technology, it’s hand-waving and tap-dancing trying to obscure how simple the basic issue is. IMHO. Okay, I’m done, I’m sorry I sounded so grumpy and took up so much comment space. I won’t take up more.

That was the last thing I expected to find out was controversial. Yes, we listen to music with our ears. Unless you’re listening at volumes that actually damage your ears, your listening content does not actually destroy your ability to perceive sound. I don’t think David is doing proper double-blind tests here, so the *way* you test with your ears matters, too, which I left out (though here the difference turns out to be less than subtle, and it’s verifiable). But otherwise, yes, we’re talking about music produced for human hearing.

mastered_for_itunes.pdf document page 3: “Because this SRC outputs a 32-bit floating-point file, it can preserve values that might otherwise fall outside of the permitted frequency range” And we actually listen to those guys?

What, just because they don’t know the difference between frequency and amplitude? 😉

Maybe they’ve discovered a new digital audio theory…

—

haha

but nice to see Apple talking about sound quality.

still: I will only consider buying on iTunes when it is lossless audio, DRM free and with full ownership, no subscription BS, like the good old CD (bonus: free storage medium, negative: no error checking)

Latof1970

The higher bit file might allow for +dBFS levels and if that is the case frequency content of clipped signals (square waves contains frequencies outside of the upper permitted frequency range) will not be aliased and hence not cause significant distortion in the audible frequency range.

If the only thing that matters is your ears, if there are
no principles only subjective hearing, then don’t worry about anything. Even if everything you hear is garbage, then
after three days of listening your “ears” will become acclimated to garbage and
garbage will become the environment and then you will like
garbage. And what difference does it
make? You are talking about Apple. Apple is a corporation. Even if you held some allegiance to one or
another principle, so what? What are you
going to do? Disagree with a corporation? Fight Apple?
Get real.

Puma Klement

Dear markLouis, please mind that in this case it’s not about David Dodson’s legendary objective hearing ability but a method of him testing and describing the changes in perceived volume certain audio files used for reference undergo when played with different settings offered by a software media player (that has been adopted by a huge amount of people as their way to experience music on a daily basis – which arouses a great deal of interest in how said media player alters music played through it for everyone who’s into producing, publishing and enjoying music for/with a public of some sort.)

You’re definitely right about fatigue and accustoming of one’s sense of hearing as it is exposed to any kind of static sound environment (be it at a garbage dump or within the elysian fields) and the subjective perception of sound by the individual.
But since it’s a matter of one’s brain to process and associate sound cultural marks can be overcome ( so one’s “ears” are not doomed 🙂 ), a good rest revives worn out hearing and by years and years of intent and mindful listening, passionate working with sound and a steady flow of information through sensitive communication one’s subjective perception of sound will broaden to a range that allows being able to make pretty well informed assumptions about how similarly (or at least comparably) structured neuronal networks deal with all the noise.

Throw in some heavy number crunching, psychological and neurological research done by universities, corporations and state intelligence and the documented experiences of freaky musicians who played music for the last 35.000 years…

…and there is something to be said about how we as a species hear even if it’s the latest insights of a single individual into how iTunes encodes a mastering WAV of the next Monolake release.

In reply to “What are you going to do?”:
I know from an economic and philosophical standpoint a megacorporation can be seen as a single entity (a bit like like swarm intelligence but with human individuals as its agents) that is not bound to ethics as they apply to humans and therefore can’t be questioned nor bothered by a human individual.
But here a corporation (Apple it is) seems to question the actions of other corporations (major labels in the music industry), not by means of moral but technology mixed with marketing to increase dominance in a certain market.

Alas! 🙂 the question begging to be answered here is not “What are you going to do?” but “WTF is going on? Are the Loudness Wars going to end ?!?!?!? Does Apple have to decrease the overall volume of its software/devices in order to squeeze more hours out of their batteries or what?”

so…You, Sir, get real because it’s the only difference You can make 🙂
Have a good one!

markLouis

Isn’t this issue vastly more simple than these long-winded (mine included) comments imply?

1) If it’s an issue of principle, then people like Gail Zappa and Neil Young are right and we just need a radically different, much higher standard for audio files/audio playback. (But that seems impossible because it would cost a lot more for devices and consumers at large seem satisfied with the status quo.)

2) Since it is effectively subjective then, there’s little to worry about because trivial tweaks to the status quo mean nothing to a) drunks in clubs listening to bad sound systems; b) cruisers in cars with giant bass speakers in the trunk shaking the car; and c) yuppies playing a ‘soundtrack for their life’ through $2 ear-buds.

I get grumpy (sorry) because I LIKE philosophical discussions but stuff like this is like faux philosophy, because it is all so straightforward that the real discussion isn’t philosophy or technology, it’s hand-waving and tap-dancing trying to obscure how simple the basic issue is. IMHO. Okay, I’m done, I’m sorry I sounded so grumpy and took up so much comment space. I won’t take up more.

That was the last thing I expected to find out was controversial. Yes, we listen to music with our ears. Unless you’re listening at volumes that actually damage your ears, your listening content does not actually destroy your ability to perceive sound. I don’t think David is doing proper double-blind tests here, so the *way* you test with your ears matters, too, which I left out (though here the difference turns out to be less than subtle, and it’s verifiable). But otherwise, yes, we’re talking about music produced for human hearing.

David Viens

mastered_for_itunes.pdf document page 3: “Because this SRC outputs a 32-bit floating-point file, it can preserve values that might otherwise fall outside of the permitted frequency range” And we actually listen to those guys?

What, just because they don’t know the difference between frequency and amplitude? 😉

Maybe they’ve discovered a new digital audio theory…

—

haha

but nice to see Apple talking about sound quality.

still: I will only consider buying on iTunes when it is lossless audio, DRM free and with full ownership, no subscription BS, like the good old CD (bonus: free storage medium, negative: no error checking)

Latof1970

The higher bit file might allow for +dBFS levels and if that is the case frequency content of clipped signals (square waves contains frequencies outside of the upper permitted frequency range) will not be aliased and hence not cause significant distortion in the audible frequency range.

And today this is even more true. Last year, the ITU agreed international standard methods of measuring loudness, and recommended guidelines for broadcast – these are being adopted and even becoming law already. So soon, you’ll see the effects of this everywhere.

I just posted a video demonstrating how it works, and some metering plugins to help you measure the effect on your own music, here:

I don’t like the effect of this within an album – I think sound check may be updated to solve this issue, and I hope Spotify will follow suit – and, there are questions about whether Simon and Garfunkel should be heard a the same average level as Meshuga. But in fact, FM compression mean this is how we’ve been hearing things for years, so. I doubt there will be too many complaints.

I’ve been using Replay Gain on my library for a long time (I’m always listening on shuffle so I do track analysis). I tried Sound Check which is supposed to do the same thing but it’s unfortunately inferior. I say unfortunately because I otherwise enjoy managing my library with iTunes. There’s iVolume and beaTunes, both of which overwrite Sound Check data with Replay Gain data, but those values aren’t transmitted via iTunes match if the track does indeed get matched (the data does move along with files that aren’t matched). 1st world problems and it could all be solved if Apple improved Sound Check, but fat chance getting them to listen.

It’s cool that Spotify uses replay gain, and it’s also great how easy it is for indie artists to get into the Spotify catalog. For me the downside of Spotify is that I can’t DJ with tracks from the service, while iTunes lets me drag the files out to whatever decks I’m using.

Anyway, Ian, I agree, normalization is great for listeners over all… people might still rev for loudness for the situations where users aren’t normalizing their files… but hopefully normalization does indeed kill the war.

And today this is even more true. Last year, the ITU agreed international standard methods of measuring loudness, and recommended guidelines for broadcast – these are being adopted and even becoming law already. So soon, you’ll see the effects of this everywhere.

I just posted a video demonstrating how it works, and some metering plugins to help you measure the effect on your own music, here:

I don’t like the effect of this within an album, personally – I think sound check may be updated to solve this issue, and I hope Spotify will follow suit – and, there are questions about whether Simon and Garfunkel should be heard a the same average level as Meshuggah. But in fact, FM compression means this is how we’ve been hearing things for years, so I doubt there will be too many complaints.

I’ve been using Replay Gain on my library for a long time (I’m always listening on shuffle so I do track analysis). I tried Sound Check which is supposed to do the same thing but it’s unfortunately inferior. I say unfortunately because I otherwise enjoy managing my library with iTunes. There’s iVolume and beaTunes, both of which overwrite Sound Check data with Replay Gain data, but those values aren’t transmitted via iTunes match if the track does indeed get matched (the data does move along with files that aren’t matched). 1st world problems and it could all be solved if Apple improved Sound Check, but fat chance getting them to listen.

It’s cool that Spotify uses replay gain, and it’s also great how easy it is for indie artists to get into the Spotify catalog. For me the downside of Spotify is that I can’t DJ with tracks from the service, while iTunes lets me drag the files out to whatever decks I’m using.

Anyway, Ian, I agree, normalization is great for listeners over all… people might still rev for loudness for the situations where users aren’t normalizing their files… but hopefully normalization does indeed kill the war.

kent williams

I do some mastering work myself; I do it cheap for friends and friends of friends because I don’t have a fancy mastering suite. But I do take it seriously.

In setting volume levels, I work by ear, for the most part, because I know my playback system

chaircrusher

I do some mastering work myself; I do it cheap for friends and friends of friends because I don’t have a fancy mastering suite. But I do take it seriously.

In setting volume levels, I work by ear, for the most part, because I know my playback system and what a good target volume sounds like, but I always check with the software to know where I’m at in absolute terms.

My volume targets are based on measuring a large number of tracks from commercial CDs. My observation with those is that if they’re modern recordings, they usually average about -12.5dB RMS over the whole track. That, coincidentally is a good target level if you don’t want to kill the dynamics but want a healthy overall level when comparing with other commercial CDs.

For dynamic material — with long quiet passages — this is a terrible goal, since it means smashing the living shit out of the louder sections to reach that average level. In that case, my alternative rule applies, which is to master so that the loud sections of the track come in around -10dB RMS.

But if you actually care about the music you have to be willing to make decisions track by track. My mastering nightmare is when people give me tracks and they’re already running so hot and squashed there’s nothing I can do to them. If they’re not willing to go back and re-do the mixdowns without blindly applying excessive limiting, I end up turning the track down, and usually applying some corrective EQ (often De-Essing, since the percussive attacks will pick up some pronounced ‘ch’ noise if they’re over-limited). So people will end up pressing a CD (or encoding MP3s) where the peak level is several dB below zero.

As for this Apple volume tweaking, I never really noticed it. You have to listen pretty closely to distinguish between a track playing back at -12dB RMS and -15dB RMS. Keep in mind that 6dB change is a perceptual doubling of volume, and 1dB difference was calibrated to be the minimum noticeable change in volume with test subjects.

Bottom line? Mix well — make it sound good in the monitors with no limiting on the master bus. Then master gently, increasing overall volume just enough to compete with other properly mastered records. Don’t bother trying to compete with the crazy BRICK WAVEFORM mastering jobs some people go for. Their music is almost always crap anyway.

teej

For those who are curious about what this thing is actually doing: Right-click on the droplet and choose Show Package Contents. Navigate into the Scripts folder. In there you will find the (fairly simple) AppleScript that powers this thing. It’s pretty much doing some shell scripts for the encoding. Might be able to tweak it to your liking.

teej

For those who are curious about what this thing is actually doing: Right-click on the droplet and choose Show Package Contents. Navigate into the Scripts folder. In there you will find the (fairly simple) AppleScript that powers this thing. It’s pretty much doing some shell scripts for the encoding. Might be able to tweak it to your liking.

Good post! Some questions/comments:- My main question is how does the encoding sound? Obviously the Mastered for iTunes droplet/afconvert isn’t intended to master recordings – when you encode a song, you expect to get back a song that sounds as close to the original as possible at the target bit rate/quality setting. – So how do Mastered for iTunes files compare (w/Sound Check off) to the original 24/96 (or whatever) files and to files converted the usual way – best SRC one has available > best dither (or HQ D>A>D) > 16/44.1 > iTunes Plus in iTunes ? Apple’s AURoundTripAAC looks like it’ll provide an easy way to ABX test the resulting files – anyone try it yet? I plan to make some comparisons using official & audience 24/96 concert recordings (mostly Phish) some time soon (doubt I’ll be able to tell the difference w/my current level of gear/skill but both will improve over time).- A free iTunes script that uses afconvert to convert alac/aiff/wav > Mastered for ITunes files (and preserves tags) would be much appreciated (doug? someone else? me, if I learn how?)- A future with non-overcompressed releases and optional end-user dynamics processing (maybe that’s not the right term for Sound Check, ReplayGain, etc.) would seem to be ideal – leading to options like having more compression for the car, less for the iPhone outside, none at home, none ever…- You can easily check how much Sound Check changes a song’s volume by enabling Sound Check in iTunes & looking in Get Info > Summary > Volume. For the songs I have:Tori Amos Teenage Hustling -6.5 dBTori Amos Blood Roses -1.5 dBSun Ra Sea of Sounds (Space Is The Place album) -6.2 dBNine Inch Nails The Great Destroyer -8.2 dB

– Presumably the change in volume would differ a bit for Mastered for iTunes files vs. iTunes encoded files – would be interesting to see what the difference is (if any). – Sound Check doesn’t seem to sound very good/work very well, and there’s the issue of preserving consistent volume w/in albums. The Mastered for iTunes doc says it’s possible to Sound Check by album but doesn’t say how (maybe there’s a gapless album setting in iTunes Producer that’s linked to Sound Check processing or something). – Have been thinking of trying iVolume (http://www.mani.de/en/ivolume/help.html) which re-analyzes tracks in iTunes, replaces the original Sound Check data w/more accurate info and supports adjustment by album. Anybody try this, and if so, does it work well? (I have no connection to the developer)- A bit depth (“sample size” in iTunes) is shown for alac/aiff/wav files in iTunes but not for aac/mp3 files. I always assumed if you started with a 16 bit uncompressed file the resulting aac/mp3 file would be 16 bit too (and that 24 bit files would probably just get truncated in most cases). Am I missing something here?

– My main question is how does the encoding sound? Obviously the Mastered for iTunes droplet/afconvert isn’t intended to master recordings – when you encode a song, you expect to get back a song that sounds as close to the original as possible at the target bit rate/quality setting.

– So how do Mastered for iTunes files compare (w/Sound Check off) to the original 24/96 (or whatever) files and to files converted the usual way – best SRC one has available > best dither (or HQ D>A>D) > 16/44.1 > iTunes Plus in iTunes ? Apple’s AURoundTripAAC looks like it’ll provide an easy way to ABX test the resulting files – anyone try it yet? I plan to make some comparisons using official & audience 24/96 concert recordings (mostly Phish) some time soon (doubt I’ll be able to tell the difference w/my current level of gear/skill but both will improve over time).

– A future with non-overcompressed releases and optional end-user dynamics processing (maybe that’s not the right term for Sound Check, ReplayGain, etc.) would seem to be ideal – leading to options like having more compression for the car, less for the iPhone outside, none at home, none ever…

– You can easily check how much Sound Check changes a song’s volume by enabling Sound Check in iTunes & looking in Get Info > Summary > Volume. For the songs I have:

– Presumably the change in volume would differ a bit for Mastered for iTunes files vs. iTunes encoded files – would be interesting to see what the difference is (if any).

– Sound Check doesn’t seem to sound very good/work very well, and there’s the issue of preserving consistent volume w/in albums. The Mastered for iTunes doc says it’s possible to Sound Check by album but doesn’t say how (maybe there’s a gapless album setting in iTunes Producer that’s linked to Sound Check processing or something).

– Have been thinking of trying iVolume ( http://www.mani.de/en/ivolume/index.html ) which re-analyzes tracks in iTunes, replaces the original Sound Check data w/more accurate info and supports adjustment by album. Anybody try this, and if so, does it work well? (I have no connection to the developer)

– A bit depth (“sample size” in iTunes) is shown for alac/aiff/wav files in iTunes but not for aac/mp3 files. I always assumed if you started with a 16 bit uncompressed file the resulting aac/mp3 file would be 16 bit too (and that 24 bit files would probably just get truncated in most cases). Am I missing something here?

Aaron

So now Apple are responsible for the end of the Loudness wars? I’ve heard it all. Apple and their shitty little earbuds are as much to blame for the squashing of music as anyone else in the industry, probably more. The rise of the loudness wars has increased alongside digital sales and delievery of music. This is no coincidence.

iTunes auto-normalizing songs in its library is no impressive feat or important by any means and will not make an impression on mastering. It is tantamount to the Auto-Bass, Auto-Level, Bass Boost, Surround Sound, worthless features of crap consumer products and listening devices. Today’s iTunes Sound Check is yesterday’s SRS.

Another item being entirely looked over is that streaming services that already utilize their own normalisation are just that. Streaming services. Designed in general for crappy computer sound systems, consumer headphones and mobile devices.

Also, it’s not as if iTunes is the first Multimedia Library Manager that has it’s own auto-normalization so that all audio plays back at an even keel for the listeners. Not by a longshot. The only difference here is, as usual, Apple is far more intrusive about it.

How about instead of attempting to give Apple major credos for an imaginary impact that will never happen, we accept this as what it is.. nothing significant.

The only way the future will change is when all the poorly educated, pooly opinioned, and poorly experienced audio engineers/mastering studios and the labels employing them wise up. iTunes trivialities are not the way this is going to happen.

I agree generally with your comments about normalization, but I don’t think you can fault Apple for Loudness Wars when the iPod is only around for the last decade. All the evidence is that this coincides with the rise of corporate-consolidated FM radio, if anything. It’s certainly not a result of *online* digital distribution – things begin with the CD.

Foljs

Yes, you hate Apple, we got that. Can you get back to the point?

Aaron

Never said I hate Apple. I own several Apple products. I just find it disgusting when people rush to give them undue credit, which happens alot.

hz

before you start calling other people poorly educated and poorly ‘opinioned’ (sic.), maybe you should learn how to read & write yourself.

Foljs

“””Also, it’s not as if iTunes is the first Multimedia Library Manager that has it’s own auto-normalization so that all audio plays back at an even keel for the listeners. Not by a longshot. The only difference here is, as usual, Apple is far more intrusive about it.”””
No, the only difference is hundreds of millions of people use Apple iPods/iPhones and iTunes, with iPod being by far the most popular portable music device, whereas all the other “first” companies are not that important.

Plus, IIRC, you have Apple to also thank about the removal of the DRM from music files.

Btw, isn’t the iTunes Store the #1 music retailer in the US the last couple of years?

Aaron

Thank Apple for the removal of DRM? They were late to that party. I’m happy they did it in regards to iTunes, but thats it. They didn’t lead the call, consumers and competitors did. ‘#1 retailer’ has to do with what exactly other than reinforcing what I already said? Regardless, I, like I assume most ppl that post on CDM… buy most my music elsewhere. Not because iTunes sucks or anything, but because a majority of what I listen to regularlly either isn’t on there, or can be bought directly from the artist or the artist’s label.. cutting out the middle man and giving all the proceeds to those involved in the creation.

The loudness war predates iTunes by many years. Apple had nothing to do with it. And yes, earbuds in general aren’t as good as large style headphones but Apple’s are among the best out there. There are dozens of different brands of earbuds that are vastly worse than Apple’s.

Aaron

So now Apple are responsible for the end of the Loudness wars? I’ve heard it all. Apple and their shitty little earbuds are as much to blame for the squashing of music as anyone else in the industry, probably more. The rise of the loudness wars has increased alongside digital sales and delievery of music. This is no coincidence.

iTunes auto-normalizing songs in its library is no impressive feat or important by any means and will not make an impression on mastering. It is tantamount to the Auto-Bass, Auto-Level, Bass Boost, Surround Sound, worthless features of crap consumer products and listening devices. Today’s iTunes Sound Check is yesterday’s SRS.

Another item being entirely looked over is that streaming services that already utilize their own normalisation are just that. Streaming services. Designed in general for crappy computer sound systems, consumer headphones and mobile devices.

Also, it’s not as if iTunes is the first Multimedia Library Manager that has it’s own auto-normalization so that all audio plays back at an even keel for the listeners. Not by a longshot. The only difference here is, as usual, Apple is far more intrusive about it.

How about instead of attempting to give Apple major credos for an imaginary impact that will never happen, we accept this as what it is.. nothing significant.

The only way the future will change is when all the poorly educated, pooly opinioned, and poorly experienced audio engineers/mastering studios and the labels employing them wise up. iTunes trivialities are not the way this is going to happen.

I agree generally with your comments about normalization, but I don’t think you can fault Apple for Loudness Wars when the iPod is only around for the last decade. All the evidence is that this coincides with the rise of corporate-consolidated FM radio, if anything. It’s certainly not a result of *online* digital distribution – things begin with the CD.

Foljs

Yes, you hate Apple, we got that. Can you get back to the point?

Aaron

Never said I hate Apple. I own several Apple products. I just find it disgusting when people rush to give them undue credit, which happens alot.

hz

before you start calling other people poorly educated and poorly ‘opinioned’ (sic.), maybe you should learn how to read & write yourself.

Foljs

“””Also, it’s not as if iTunes is the first Multimedia Library Manager that has it’s own auto-normalization so that all audio plays back at an even keel for the listeners. Not by a longshot. The only difference here is, as usual, Apple is far more intrusive about it.”””
No, the only difference is hundreds of millions of people use Apple iPods/iPhones and iTunes, with iPod being by far the most popular portable music device, whereas all the other “first” companies are not that important.

Plus, IIRC, you have Apple to also thank about the removal of the DRM from music files.

Btw, isn’t the iTunes Store the #1 music retailer in the US the last couple of years?

Aaron

Thank Apple for the removal of DRM? They were late to that party. I’m happy they did it in regards to iTunes, but thats it. They didn’t lead the call, consumers and competitors did. ‘#1 retailer’ has to do with what exactly other than reinforcing what I already said? Regardless, I, like I assume most ppl that post on CDM… buy most my music elsewhere. Not because iTunes sucks or anything, but because a majority of what I listen to regularlly either isn’t on there, or can be bought directly from the artist or the artist’s label.. cutting out the middle man and giving all the proceeds to those involved in the creation.

zerobeat

The loudness war predates iTunes by many years. Apple had nothing to do with it. And yes, earbuds in general aren’t as good as large style headphones but Apple’s are among the best out there. There are dozens of different brands of earbuds that are vastly worse than Apple’s.

Wouter Dullaert

So if I get this right “mastered for itunes” is just an encoder profile to create good aac’s or mp3’s, which have some volume profile metadata encoded? It doesn’t seem like such a big deal.

I can see the value in specific mastering, but not like this. Mastering a radio edit differently than the album track makes sense, because most people listen radio on small speakers with very little bass response, while for a CD you can assume that people will want to play it back on a decent audio system. This might call for different tradeoffs at the mastering stage.
Similarly I understand that you master different for vinyl and CD because of both have different technical limitations. In a sense you could also master differently for mp3 or AAC (if you are given an encoder profile because different encoders and settings can have different effects on the end result).

The thing is, I feel like we should just do away with the lossy codecs. Technology has come to the point where both the bandwidth and storage requirements for lossless encoding of CD spec audio (16bit/44.1kHz) is perfectly feasible. This would do away with the need for any specific “mastered for mp3” stuff. You’d just master the track as you would for CD and encode to FLAC or ALAC. Encoder settings would only impact file size and not sound quality.
Apple could then still release a toolset for encoding files, and provide a encoding/metadata standard, just to make sure everything works as it should. But don’t call it “mastered for itunes”, call it “iTunes Ready” or something, because it’s not mastering.

I agree, the worry I’d have with this is that if it becomes the standard this year or next, we’ll be in the same position again in 3 years except instead of saying how much we hate mp3’s we’ll just replace it with AAC. I think we’re right on the edge of being able to do away with lossy codecs, and should just make the push for lossless.

Wouter Dullaert

So if I get this right “mastered for itunes” is just an encoder profile to create good aac’s or mp3’s, which have some volume profile metadata encoded? It doesn’t seem like such a big deal.

I can see the value in specific mastering, but not like this. Mastering a radio edit differently than the album track makes sense, because most people listen radio on small speakers with very little bass response, while for a CD you can assume that people will want to play it back on a decent audio system. This might call for different tradeoffs at the mastering stage.
Similarly I understand that you master different for vinyl and CD because of both have different technical limitations. In a sense you could also master differently for mp3 or AAC (if you are given an encoder profile because different encoders and settings can have different effects on the end result).

The thing is, I feel like we should just do away with the lossy codecs. Technology has come to the point where both the bandwidth and storage requirements for lossless encoding of CD spec audio (16bit/44.1kHz) is perfectly feasible. This would do away with the need for any specific “mastered for mp3” stuff. You’d just master the track as you would for CD and encode to FLAC or ALAC. Encoder settings would only impact file size and not sound quality.
Apple could then still release a toolset for encoding files, and provide a encoding/metadata standard, just to make sure everything works as it should. But don’t call it “mastered for itunes”, call it “iTunes Ready” or something, because it’s not mastering.

I agree, the worry I’d have with this is that if it becomes the standard this year or next, we’ll be in the same position again in 3 years except instead of saying how much we hate mp3’s we’ll just replace it with AAC. I think we’re right on the edge of being able to do away with lossy codecs, and should just make the push for lossless.

clabbored buttermilk shake

isnt there a software that lets you put in the music and then you tell it where you will be listening to it for example car stereo, home theater, ipod,club, etc. and then it produces results that match each source

clabbored buttermilk shake

isnt there a software that lets you put in the music and then you tell it where you will be listening to it for example car stereo, home theater, ipod,club, etc. and then it produces results that match each source

prow

Re. the concluding paragraph: you can push audio “into the red” without them actually reaching 0dB peaks, using limiters (like the author correctly mentions earlier). So you can always achieve that effect if you’re into it, while sticking to the -15dB RMS standard… and hey, what’s wrong with some extra headroom?

I agree with Kent Williams re. the danger of ruining richly dynamic content by blindly sticking to the RMS rule for a whole track. But I think it’s a step forward towards more sensible mastering jobs across the board.

prow

Re. the concluding paragraph: you can push audio “into the red” without them actually reaching 0dB peaks, using limiters (like the author correctly mentions earlier). So you can always achieve that effect if you’re into it, while sticking to the -15dB RMS standard… and hey, what’s wrong with some extra headroom?

I agree with Kent Williams re. the danger of ruining richly dynamic content by blindly sticking to the RMS rule for a whole track. But I think it’s a step forward towards more sensible mastering jobs across the board.

Sorry for digging up an old post, and this is off topic too, I’m just wondering where could I get such clip or tools for your earphone conversion? I don’t know much about audio equipments and I’ve found this really neat!

Other question is if it has an effect on the audio quality since it uses the apple earphone/wire? Thanks!

Sorry for digging up an old post, and this is off topic too, I’m just wondering where could I get such clip or tools for your earphone conversion? I don’t know much about audio equipments and I’ve found this really neat!

Other question is if it has an effect on the audio quality since it uses the apple earphone/wire? Thanks!

Denny

Thank you for your detailed and well-written article. I am setting the gain for my car audio amplifiers using sine wave test tones at 0dB and a digital multimeter. I noticed that the test tones played much louder from a CD than from my iPhone. I can conclude from your research that it’s Sound Check getting in the way of proper system calibration. I had assumed it would bring tracks up in volume until they peaked at 0dB; not down to an average RMS level. I’ll try again tomorrow, this time with Sound Check off for good.

Denny

Thank you for your detailed and well-written article. I am setting the gain for my car audio amplifiers using sine wave test tones at 0dB and a digital multimeter. I noticed that the test tones played much louder from a CD than from my iPhone. I can conclude from your research that it’s Sound Check getting in the way of proper system calibration. I had assumed it would bring tracks up in volume until they peaked at 0dB; not down to an average RMS level. I’ll try again tomorrow, this time with Sound Check off for good.

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